It is my long-range goal to elucidate on a subcellular and molecular level the mechanism by which catecholamines regulate cardiac adenylate cyclase and thereby influence myocardial activities. It is the specific purpose of this grant to: 1) Purify myocardial adenylate cyclase; 2) Characterize it both physiochemically and enzymatically (kinetically); and 3) Study regulatory aspects of adenylate cyclase.